It is desirable to reduce the temperature of chickens and other type poultry after the birds have been processed, are defeathered, eviscerated and are otherwise oven-ready and before the birds are packaged for delivery to the retail customer. A conventional poultry chiller is the "auger type" chiller which includes a trough-shaped half-round tank filled with ice water in which the auger provides positive movement of the birds through the tank. The cooling effect for the water and the birds was originally provided by crushed ice added to the water. The later designs include a counter-flow recirculation of the chilled water through the tank, with the water being chilled by a refrigerated heat exchanger instead of using ice. The water is introduced at one end of the tank and flows progressively to the other end, where it is recirculated. In the meantime, the birds are continually delivered to the tank and moved under the influence of the auger in the counter-flow direction, and are lifted from the delivery end of the tank for further processing. A prior art poultry chiller of this general type is disclosed in U.S. Pat. No. 5,868,000, and a heat exchanger for the water refrigeration system suitable for this purpose is shown in U.S. Pat. No. 5,509,470.
The trough-shaped tanks of the chillers can be five to ten feet in diameter. The United States Department of Agriculture rules require one-half gallon of fresh makeup water to be added to the chiller for each bird that is processed through the chiller, which is 70 gallons per minute for a processing line that moves 140 birds per minute. The fresh makeup water is added to the tank at the delivery end of the tank, where the birds have been chilled and are being lifted out of the tank. The water flows against the birds in the opposite direction of movement of the birds and the auger of the tank, and the water overflows at the bird inlet end of the tank, assuring that the birds are always flowing into the cleanest water and that there is always a temperature drop between the temperature of each bird and the temperature of the water about each bird.
One of the problems of counter-flowing the refrigerated water through the tank is that the auger, by its rotation as it moves the birds forward, also pushes approximately the same volume of water toward the bird outlet end, along with the birds. The water must find its way back in counter-flow direction with respect to the birds and to the moving surfaces of the auger.
It is desirable that the augers of the chillers utilize solid auger flights so as to prevent the birds becoming trapped or hanging against the auger and not moving properly through the tank, and to avoid damaging the birds. Because of the desirability to employ augers with solid flights, the accepted way to move the water through the tank in a counter-flow direction with respect to both the auger and the birds is to flow the water around the outside perimeter of the auger flights, between the auger and the facing surface of the tank, which is normally limited to a small dimension, such as between 1 inch and 11/2 inches clearance space. This small space at the perimeter of the auger avoids having the smaller birds becoming caught or trapped between the auger and the tank, and avoids damage to the birds.
Usually, the auger of the chiller has a 360.degree. flight every 4 linear feet of the auger. Therefore, the water is required to flow about the peripheries of several auger flights when moving along the tank.
In addition to the critical restriction of water flow through this narrow restriction between the perimeter of the auger flights and the facing surface of the tank there is an additional restriction at the perimeter of the auger blades by the birds which tend to follow the path of the water about the blade and partially block the perimeter opening about the auger blades. This significantly limits the amount of water that can be circulated through the birds at this position in the tank, thereby resulting in inadequate cooling of the birds.
Also, since the counter-flow water movement that occurs in this arrangement flows only around the edges of the flights of the auger, and not uniformly through the mass of birds at the centerline of the tank, there is a lack of uniformity and effectiveness in chilling the birds that are at the centerline of the tank or which are "clumped" or clustered together in the tank. Typically, most of the birds will migrate toward one sidewall of the tank because of frictional contact with the rotating auger, leaving the opposite side of the tank with fewer birds, and the major circulation of water is about the edges of the auger flight that is free of birds and therefore open for water movement.
Another problem with the typical prior art auger driven poultry chiller is that when the operation of the processing line which delivers birds to the chiller is being progressively terminated between shifts of the workers in the plant, by terminating the introduction of birds to the processing line and allowing the birds already on the line to move through the line, the absence of delivery of birds to the chiller tank in combination with the removal of birds from the delivery end of the tank results in less volume of birds and water in the tank, causing a reduction in the water level of the tank. This means that the water has even less space to pass around the perimeter of the auger blade to the next segment of the tank, resulting in starving the downstream segments of the tank of water. The reduction of supply of water in the last segment of the tank may result in starving the circulating pump of water.
It is to the above noted problems of the prior art that this invention is directed.